Synergistic antimicrobial compositions containing 2-(thiocyanomethylthio) benzothiazole and an organic acid

ABSTRACT

Compositions comprising 2-(thiocyanomethylthio)benzothiazole and at least one organic acid or its salt are disclosed which are synergistically effective compared to the respective components alone in controlling the growth of microorganisms in or on a material or medium. Methods to control the growth of microorganisms and prevent spoilage caused by microorganisms with the use of the compositions of the present invention are also disclosed.

This is a division of application Ser. No. 08/125,849, filed Sep. 24, 1993, now U.S. Pat. No. 5,494,904.

The present invention relates to certain compositions and processes useful for controlling the growth of one or more microorganisms and for preventing spoilage caused by bacteria and fungi in various products, materials, or media, particularly industrial products, materials or media. These materials or media include wood pulp, wood chips, lumber, adhesives, coatings, animal hides, paper mill liquors, pharmaceutical formulations, cosmetics and toiletry formulations, geological drilling lubricants, agrochemical compositions, paints, leathers, wood, metalworking fluids, cooling tower water, tanning liquors, starch, petrochemicals, proteinaceous materials, acrylic latex paint emulsions, and textiles. The novel processes and mixtures of the present invention show unexpected synergistic activity against microorganisms, including bacteria and fungi. Specifically, the invention is directed to the use of compositions comprising 2-(thiocyanomethylthio)benzothiazole and at least one organic acid or salt thereof.

Many of the products, materials, or media referred to above, when wet or subjected to treatment in water, are susceptible to bacterial and/or fungal deterioration or degradation unless steps are taken to inhibit such degradation or deterioration.

To control deterioration or degradation caused by microorganisms, various industrial microbicides are used. Workers in the trade have continued to seek improved biocides that have low toxicity and are capable of exhibiting a prolonged biocidal effect at normal use levels.

Organic acids can be used alone to control microorganisms, but many of them have low efficacy against bacteria and fungi unless extremely high concentrations are used. 2-(Thiocyanomethylthio)benzothiazole (TCMTB) can also be used alone in low concentrations as a biocide.

It is an object of this invention to provide a microbicidal composition capable of controlling the growth of at least one microorganism, particularly fungi and bacteria, over prolonged periods of time. It is an additional object to provide such compositions which are economical to use. Methods of controlling the growth of at least one microorganism are also objects of this invention.

The present invention provides a composition comprising 2-(thiocyanomethylthio)-benzothiazole and at least one organic acid or its salt, where the components are present in a combined amount synergistically effective to control the growth of at least one microorganism.

The present invention also provides a method for controlling the growth of at least one microorganism in or on a material or medium susceptible to attack by the microorganism which comprises the step of adding to the material or medium a composition of the present invention in an amount synergistically effective to control the growth of the microorganism. The synergistically effective amount varies in accordance with the material or medium to be treated and can, for a particular application, be routinely determined by one skilled in the art.

The present invention also embodies the separate addition of 2-(thiocyanomethylthio)benzothiazole and at least one organic acid or its salt to the products, materials or media described above. According to this embodiment, the components are individually added to the system so that the final amount of 2-(thiocyanomethylthio)benzothiazole and at least one organic acid or its salt present in the system at the time of use is that amount synergistically effective to control the growth of at least one microorganism.

The compositions of the present invention are also useful in preserving various types of industrial media or materials susceptible to attack by microorganisms. Such media or materials include but are not limited to dyes, pastes, lumber, leather, textiles, pulp, wood chips, tanning liquors, paper mill liquors, polymer emulsions, paints, metalworking fluids, geological drilling lubricants, cooling water systems, pharmaceutical formulations, cosmetics and toiletry formulations.

The composition can also be useful in agrochemical formulations for the purpose of protecting seeds or crops against microbial spoilage.

Additional objects and advantages of the present invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by the practice of the present invention. The objects and advantages of the present invention may be realized and obtained by means of the elements and combinations particularly pointed out in the claims.

It is to be understood that both the foregoing general description and the following general description are exemplary and explanatory only and are not restrictive of the present invention as claimed.

When two chemical microbicides are combined into one product or added separately three results are possible:

1) The resulting product would produce an additive (neutral) effect.

2) The products in the product would produce an antagonistic effect, or

3) The chemicals in the product would produce a synergistic effect.

An additive effect has no economic advantage over the individual components. The antagonistic effect would produce a negative impact. Only a synergistic effect, which is less likely than either an additive or antagonistic effect, would produce a positive effect and therefore possess economic advantages.

The microbicidal compositions combining 2-(thiocyanomethylthio)benzothiazole and at least one organic acid or its salt demonstrate an unexpected synergistic effect compared to the respective components alone. Thus, these compositions achieve superior, i.e. greater than additive, microbicidal activity at low concentrations against a wide variety of microorganisms. Examples of microorganisms include fungi and bacteria such as Trichoderma viride and Pseudomonas aeruginosa. Preferably, the compositions of the present invention have a low toxicity.

The preparation of 2-(thiocyanomethylthio)benzothiazole (TCMTB) is described in U.S. Pat. No. 3,520,976. TCMTB is commercially available and also easily synthesized from commercially available raw materials.

The organic acid can be any organic acid that will produce a synergistic effect when combined with 2-(thiocyanomethylthio)benzothiazole. Examples include aromatic organic acids, cyclic organic acids, aliphatic organic acids or their salts. Specific examples of effective organic acids include dehydroacetic acid, octanoic acid, nonanoic acid, formic acid, sorbic acid, acetic acid, oxalic acid, glycolic acid, citric acid, gluconic acid, malic acid, propionic acid, lauric acid, undecylenic acid, benzoic acid or derivatives of benzoic acid such as 2-hydroxybenzoic acid, 3-hydroxybenzoic acid or 4-hydroxybenzoic acid. The salts of the organic acids, particularly those containing calcium, zinc, potassium, or sodium may also be used. Further, mixtures of organic acids can also be used. When such mixtures are used in combination with TCMTB, at least one of the organic acids in the mixtures has a synergistic relationship with the TCMTB. Organic acids useful in the invention are commercially available or may be synthesized from commercially available raw materials.

The organic acid may be chosen based on the compatibility with the materials or media. Compatibility is determined by criteria such as solubility in the fluid system and lack of reactivity with the fluid, material, or media in question. The compatibility is readily determined by one having ordinary skill in the art by adding the organic acid to the material or media to be used. When used in a fluid system it is preferable that the organic acid be freely soluble in the particular fluid resulting in a uniform solution or dispersion.

In the following discussion of preferred embodiments, component (a) is 2-(thiocyanomethylthio)benzothiazole and component (b) is an organic acid or its salt.

As described above, components (a) and (b) are used in synergistically effective amounts. The weight ratios of (a) to (b) vary depending on the type of microorganisms, material, or media to which the composition is applied. One skilled in the art can readily determine without undue experimentation, the appropriate weight ratios for a specific application. Generally, the ratio of component (a) to component (b) preferably ranges from 1:99 to 99:1, more preferably from 1:30 to 30:1, and most preferably from 1:5 to 5:1.

The following weight ratios of TCMTB to the following organic acids are also preferred:

    ______________________________________                                         TCMTB:sodium benzoic acid                                                                             2:1 to 1:555                                            TCMTB:sodium benzoate  1:2.5 to 0.1:133                                        TCMTB:p-hydroxybenzoic acid                                                                           2:1 to 0.1:266                                          TCMTB:sodium 2-hydroxybenzoate                                                                        1:8 to 1:166                                            TCMTB:dehydroacetic acid                                                                              2:1 to 1:100                                            TCMTB:sodium dehydroacetate                                                                           1:5 to 1:67                                             TCMTB:octanoic acid    2:1 to 1:266                                            TCMTB:nonanoic acid    2:1 to 1:266                                            TCMTB:formic acid      1:2.5 to 1:133                                          TCMTB:sorbic acid      2:1 to 1:100                                            TCMTB:potassium sorbate                                                                               1:100 to 1:700                                          TCMTB:acetic acid      1:3 to 0.1:300                                          TCMTB:oxalic acid      2:1 to 1:166                                            TCMTB:glycolic acid    1:2.5 to 1:666                                          TCMTB:citric acid      1:5 to 1:166                                            TCMTB:gluconic acid    1:20 to 1:500                                           TCMTB:malic acid       1:2.5 to 1:666                                          TCMTB:propionic acid   1:1 to 0.1:133                                          TCMTB:sodium propionate                                                                               0.1:177 to 1:666                                        TCMTB:lauric acid      1:1 to 1:333                                            TCMTB:undecylenic acid 2:1 to 1:533                                            TCMTB:sodium undecylenate                                                                             1:20 to 0.1:100                                         ______________________________________                                    

Depending upon the specific application, the composition may be prepared in liquid form by dissolving the composition in an organic solvent. The preservative may be prepared in an emulsion form by emulsifying it in water, or if necessary, by adding a surfactant. Additional chemicals such as insecticides may be added to the foregoing preparation.

The synergistic activity of the combinations described above has been confirmed using standard laboratory techniques as illustrated below. The following examples are intended to illustrate, not limit, the present invention.

MICROBIOLOGICAL EVALUATION

A. Fungal evaluation

Mineral salts-glucose medium was used. To prepare the medium, the following ingredients were added to 1 liter of deionized water: 0.7 g of KH₂ PO₄, 0.7 g of MgSO₄.7H₂ O, 1.0 g of NH₄ NO₃, 0.005 g NaCl, 0.002 g FeSO₄.7H₂ O, 0.002 g ZnSO₄.7H₂ O, 0.001 g MmSO₄.7H₂ O, 10 g of Glucose. The pH of the medium was adjusted to 6 with 1N NaOH. The medium was distributed in 50 g amounts in 250 mL flasks and autoclaved at 121° C. for 20 minutes. The fungus, Trichoderma viride, was grown on a potato dextrose agar slant for 7 to 10 days and a spore suspension prepared by washing down the spores from the slant into a sterile saline solution. After addition of the biocides in the desired concentrations to the sterile mineral salts-glucose medium, the fungal spore suspension was added. The final spore concentration was approximately 10⁶ cfu/mL. The inoculated media was incubated at 28° C. for 14 days.

B. Bacterial evaluation

Nutrient broth (2.5 g/liter of deionized water) was prepared and the pH adjusted to 6 with 1N HCL. This was distributed in 5 mL amounts in test tubes and autoclaved for 20 minutes at 121° C. After addition of the biocides in the desired concentrations to the nutrient broth, 100 microliters of a suspension of Pseudomonas aeruginosa cells of approximately 9.3×10⁸ cfc/mL were added and incubated at 37° C. for 48 hours.

In Examples 1 through 22, a synergistic effect was demonstrated in separate experiments by testing 2-(thiocyanomethylthio)benzothiazole, designated as component A and the corresponding organic acid or its salt as component B in a series of tests in varying ratios and a range of concentrations against the fungus, Trichoderma viride and also against the bacterium, Pseudomonas aeruginosa using the methods described above.

The lowest concentration of each mixture or compound which completely prevented growth of the fungi for two weeks and the bacteria for 48 hours was taken as the end points for synergism calculations. End points for the various mixtures were then compared with the end points for the pure active ingredients alone in concomitantly prepared flasks or test tubes.

Synergism was demonstrated by the method described by Kull, E. C., Eisman, P. C., Sylwestrwicz, H. D., and Mayer, R. L. 1961. Applied Microbiology. 9: 538-541 wherein

    QA/Qa+QB/Qb is less than 1

Qa=Concentration of compound A in parts per million, acting alone, which produced an end point.

Qb=Concentration of compound B in parts per million, acting alone, which produced an end point.

QA=Concentration of compound A in parts per million, in the mixture, which produced an end point.

QB=Concentration of compound B in parts per million, in the mixture, which produced an end point.

When the sum of QA/Qa and QB/Qb is greater than one, antagonism is indicated and when the sum is equal to one, addivity is indicated. When the sum of this value is less than one, synergism exists.

This procedure for demonstrating synergism of the compositions of this invention is a widely used and acceptable procedure. More detailed information is provided in the article by Kull et al. Further information concerning this procedure is contained in U.S. Pat. No. 3,231,509, which is incorporated herein by reference.

In general, however, an effective fungicidal and bactericidal response can be obtained when the synergistic combination is employed in concentrations ranging from about 0.1 to about 3000 ppm of 2-(thiocyanomethylthio)benzothiazole, preferably 0.1 to 1000 ppm, and most preferably 0.1 to 500 ppm, and from about 0.1 to about 1% of an organic acid, preferably 0.1 to 5000 ppm and most preferably 0.1 to 2000 ppm.

    ______________________________________                                         Example 1                                                                      Component A = TCMTB                                                            Component B = Benzoic acid                                                            Quantities producing end points (ppm)                                   Test                                        Q.sub.A /Q.sub.a +                 organism Q.sub.a                                                                              Q.sub.A                                                                               Q.sub.b                                                                             Q.sub.B                                                                             Q.sub.A /Q.sub.a                                                                     Q.sub.B /Q.sub.b                                                                     Q.sub.B /Q.sub.b                   ______________________________________                                         Trichoderma                                                                              9    --     --   --   --    --    --                                 viride                                                                                  --    0.75   --   400  0.08  0.50  0.58                                        --    1.5    --   200  0.17  0.25  0.42                                        --    1.5    --   400  0.17  0.50  0.67                                        --    3      --    25  0.33  0.03  0.36                                        --    3      --    50  0.33  0.06  0.39                                        --    3      --   100  0.33  0.13  0.46                                        --    3      --   200  0.33  0.25  0.58                                        --    3      --   400  0.33  0.50  0.83                                        --    --     800  --   --    --    --                                 Pseudomonas                                                                             50    --     --   --   --    --    --                                 aeruginosa                                                                              --    1      --   100  0.02  0.4   0.42                                        --    2.5    --    50  0.05  0.2   0.25                                        --    2.5    --   100  0.05  0.4   0.45                                        --    5      --    25  0.1   0.1   0.2                                         --    5      --    50  0.1   0.2   0.3                                         --    5      --   100  0.1   0.4   0.5                                         --    10     --    5   0.2   0.02  0.22                                        --    10     --    10  0.2   0.04  0.24                                        --    10     --    25  0.2   0.1   0.3                                         --    10     --    50  0.2   0.2   0.4                                         --    10     --   100  0.2   0.4   0.6                                         --    --     250  --   --    --    --                                 ______________________________________                                    

    ______________________________________                                         Example 2                                                                      Component A = TCMTB                                                            Component B = Sodium benzoate                                                  Quantities producing end points (ppm)                                          Test                                        Q.sub.A /Q.sub.a +                 organism                                                                               Q.sub.a                                                                              Q.sub.A                                                                               Q.sub.b                                                                              Q.sub.B                                                                             Q.sub.A /Q.sub.a                                                                     Q.sub.B /Q.sub.b                                                                     Q.sub.B /Q.sub.b                   ______________________________________                                         Tricho-  9    --     --    --   --    --    --                                 derma                                                                          viride                                                                                 --    1.5    --    2000 0.17  0.67  0.84                                       --    3      --     50  0.33  0.02  0.35                                       --    3      --     100 0.33  0.03  0.36                                       --    3      --     200 0.33  0.07  0.40                                       --    3      --     400 0.33  0.13  0.46                                       --    3      --     800 0.33  0.27  0.60                                       --    3      --    1000 0.33  0.33  0.66                                       --    3      --    2000 0.33  0.67  <1                                         --    --     >3000 --   --    --    --                                 Pseudo- 50    --     --    --   --    --    --                                 monas                                                                          aeruginosa                                                                             --    10     --     25  0.2   0.03  0.23                                       --    10     --     50  0.2   0.05  0.25                                       --    10     --     100 0.2   0.1   0.3                                        --    10     --     250 0.2   0.25  0.45                                       --    10     --     500 0.2   0.5   0.7                                        --    10     --    1000 0.2   1     1.2                                        --    --     >1000 --   --    --    --                                 ______________________________________                                    

    ______________________________________                                         Example 3                                                                      Component A = TCMTB                                                            Component B = p-hydroxybenzoic acid                                                   Quantities producing end points (ppm)                                   Test                                        Q.sub.A /Q.sub.a +                 organism Q.sub.a                                                                              Q.sub.A                                                                               Q.sub.b                                                                             Q.sub.B                                                                             Q.sub.A /Q.sub.a                                                                     Q.sub.B /Q.sub.b                                                                     Q.sub.B /Q.sub.b                   ______________________________________                                         Trichoderma                                                                              9    --     --   --   --    --    --                                 viride                                                                                  --    0.75   --   2000 0.08  0.67  0.75                                        --    1.5    --   1000 0.17  0.33  0.5                                         --    1.5    --   2000 0.17  0.67  0.84                                        --    3      --    25  0.33  0.00  0.33                                        --    3      --    50  0.33  0.02  0.35                                        --    3      --    100 0.33  0.03  0.36                                        --    3      --    200 0.33  0.07  0.40                                        --    3      --    400 0.33  0.13  0.46                                        --    3      --    800 0.33  0.27  0.60                                        --    3      --   1000 0.33  0.33  0.66                                        --    3      --   2000 0.33  0.67  1                                           --    --     3000 --   --    --    --                                 Pseudomonas                                                                             50    --     --   --   --    --    --                                 aeruginosa                                                                              --    1.0    --    100 0.02  0.4   0.42                                        --    2.5    --    100 0.05  0.4   0.45                                        --    5      --    50  0.1   0.2   0.3                                         --    5      --    100 0.1   0.4   0.5                                         --    10     --     5  0.2   0.02  0.22                                        --    10     --    10  0.2   0.04  0.24                                        --    10     --    25  0.2   0.1   0.3                                         --    10     --    50  0.2   0.2   0.4                                         --    10     --    100 0.2   0.4   0.6                                         --    --      250 --   --    --    --                                 ______________________________________                                    

    ______________________________________                                         Example 4                                                                      Component A = TCMTB                                                            Component B = 2-hydroxybenzoic acid (sodium salt)                              Quantities producing end points (ppm)                                          Test                                        Q.sub.A /Q.sub.a +                 organism                                                                               Q.sub.a                                                                              Q.sub.A                                                                               Q.sub.b                                                                              Q.sub.B                                                                             Q.sub.A /Q.sub.a                                                                     Q.sub.B /Q.sub.b                                                                     Q.sub.B /Q.sub.b                   ______________________________________                                         Tricho-  9    --     --    --   --    --    --                                 derma                                                                          viride                                                                                 --     3     --     25  0.33  0.00  0.33                                       --     3     --     50  0.33  0.02  0.35                                       --     3     --     100 0.33  0.03  0.36                                       --     3     --     200 0.33  0.07  0.40                                       --     3     --     400 0.33  0.13  0.46                                       --     3     --     800 0.33  0.27  0.60                                       --     3     --    1000 0.33  0.33  0.66                                       --     3     --    2000 0.33  0.67  <1.00                                      --    --     >3000 --   --    --    --                                 Pseudo- 50    --     --    --   --    --    --                                 monas                                                                          aeruginosa                                                                             --    10     --     250 0.2   0.25  0.45                                       --    10     --     500 0.2   0.5   0.7                                        --    --     >1000 --   --    --    --                                 ______________________________________                                    

    ______________________________________                                         Example 5                                                                      Component A = TCMTB                                                            Component B = Dehydroacetic acid                                                      Quantities producing end points (ppm)                                   Test                                        Q.sub.A /Q.sub.a +                 organism Q.sub.a                                                                              Q.sub.A                                                                               Q.sub.b                                                                             Q.sub.B                                                                             Q.sub.A /Q.sub.a                                                                     Q.sub.B /Q.sub.b                                                                     Q.sub.B /Q.sub.b                   ______________________________________                                         Trichoderma                                                                              9    --     --   --   --    --    --                                 viride                                                                                  --    0.75   --   100  0.08  0.5   0.58                                        --    1.5    --   100  0.17  0.5   0.67                                        --    3.0    --    50  0.33  0.25  0.58                                        --    3.0    --   100  0.33  0.5   0.83                                        --    4.5    --    25  0.5   0.13  0.63                                        --    4.5    --    50  0.5   0.25  0.75                                        --    4.5    --   100  0.5   0.50  1                                           --    --     200  --   --    --    --                                 Pseudomonas                                                                             50    --     --   --   --    --    --                                 aeruginosa                                                                              --    2.5    --   100  0.05  0.2   0.25                                        --    2.5    --   250  0.05  0.5   0.55                                        --    5      --   100  0.1   0.2   0.3                                         --    5      --   250  0.1   0.5   0.6                                         --    10     --    5   0.2   0.01  0.21                                        --    10     --    10  0.2   0.02  0.22                                        --    10     --    25  0.2   0.05  0.25                                        --    10     --    50  0.2   0.1   0.3                                         --    10     --   100  0.2   0.2   0.4                                         --    10     --   250  0.2   0.5   0.7                                         --    --     500  --   --    --    --                                 ______________________________________                                    

    ______________________________________                                         Example 6                                                                      Component A = TCMTB                                                            Component B = Sodium dehydroacetate                                                   Quantities producing end points (ppm)                                   Test                                        Q.sub.A /Q.sub.a +                 organism Q.sub.a                                                                              Q.sub.A                                                                               Q.sub.b                                                                             Q.sub.B                                                                             Q.sub.A /Q.sub.a                                                                     Q.sub.B /Q.sub.b                                                                     Q.sub.B /Q.sub.b                   ______________________________________                                         Trichoderma                                                                              9    --     --   --   --    --    --                                 viride                                                                                  --    3      --   200  0.33  0.5   0.83                                        --    4.5    --    25  0.5   0.06  0.56                                        --    4.5    --    50  0.5   0.13  0.63                                        --    4.5    --   100  0.5   0.25  0.75                                        --    4.5    --   200  0.5   0.5   1                                           --    --     400  --   --    --    --                                 Pseudomonas                                                                             Combinations against Pseudonomas aeruginosa                           aeruginosa                                                                              were not synergistic                                                  ______________________________________                                    

    ______________________________________                                         Example 7                                                                      Component A = TCMTB                                                            Component B = Octanoic acid                                                           Quantities producing end points (ppm)                                   Test                                        Q.sub.A /Q.sub.a +                 organism Q.sub.a                                                                              Q.sub.A                                                                               Q.sub.b                                                                             Q.sub.B                                                                             Q.sub.A /Q.sub.a                                                                     Q.sub.B /Q.sub.b                                                                     Q.sub.B /Q.sub.b                   ______________________________________                                         Trichoderma                                                                              9    --     --   --   --    --    --                                 viride                                                                                  --    1.5    --   400  0.17  0.5   0.67                                        --    3      --   200  0.33  0.25  0.58                                        --    3      --   400  0.33  0.50  0.83                                        --    4.5    --    50  0.50  0.06  0.56                                        --    4.5    --   100  0.50  0.13  0.63                                        --    4.5    --   200  0.50  0.25  0.75                                        --    4.5    --   400  0.50  0.50  1                                           --    --     800  --   --    --    --                                 Pseudomonas                                                                             50    --     --   --   --    --    --                                 aeruginosa                                                                              --    1      --   250  0.02  0.5   0.52                                        --    2.5    --   100  0.05  0.2   0.25                                        --    2.5    --   250  0.05  0.5   0.55                                        --    5      --   100  0.1   0.2   0.3                                         --    5      --   250  0.1   0.5   0.6                                         --    10     --    5   0.2   0.01  0.21                                        --    10     --    10  0.2   0.02  0.22                                        --    10     --    25  0.2   0.05  0.25                                        --    10     --    50  0.2   0.1   0.3                                         --    10     --   100  0.2   0.2   0.4                                         --    10     --   250  0.2   0.5   0.7                                         --    --     500  --   --    --    --                                 ______________________________________                                    

    ______________________________________                                         Example 8                                                                      Component A = TCMTB                                                            Component B = Nonanoic acid                                                           Quantities producing end points (ppm)                                   Test                                        Q.sub.A /Q.sub.a +                 organism Q.sub.a                                                                              Q.sub.A                                                                               Q.sub.b                                                                             Q.sub.B                                                                             Q.sub.A /Q.sub.a                                                                     Q.sub.B /Q.sub.b                                                                     Q.sub.B /Q.sub.b                   ______________________________________                                         Trichoderma                                                                              9    --     --   --   --    --    --                                 viride                                                                                  --    0.75   --   200  0.08  0.5   0.58                                        --    1.5    --   200  0.17  0.5   0.67                                        --    3      --   100  0.33  0.25  0.58                                        --    3      --   200  0.33  0.5   0.83                                        --    4.5    --    50  0.5   0.13  0.63                                        --    4.5    --   100  0.5   0.25  0.75                                        --    4.5    --   200  0.5   0.5   1.0                                         --    --     400  --   --    --    --                                 Pseudomonas                                                                             50    --     --   --   --    --    --                                 aeruginosa                                                                              --    1      --   250  0.02  0.5   0.52                                        --    2.5    --   100  0.05  0.2   0.25                                        --    2.5    --   250  0.05  0.5   0.55                                        --    5      --   100  0.1   0.2   0.3                                         --    5      --   250  0.1   0.5   0.6                                         --    10     --    5   0.2   0.01  0.21                                        --    10     --    10  0.2   0.02  0.22                                        --    10     --    25  0.2   0.05  0.25                                        --    10     --    50  0.2   0.1   0.3                                         --    10     --   100  0.2   0.2   0.4                                         --    10     --   250  0.2   0.5   0.7                                         --    --     500  --   --    --    --                                 ______________________________________                                    

    ______________________________________                                         Example 9                                                                      Component A = TCMTB                                                            Component B = Formic acid                                                      Quantities producing end points (ppm)                                          Test                                        Q.sub.A /Q.sub.a +                 organism                                                                               Q.sub.a                                                                              Q.sub.A                                                                               Q.sub.b                                                                              Q.sub.B                                                                             Q.sub.A /Q.sub.a                                                                     Q.sub.B /Q.sub.b                                                                     Q.sub.B /Q.sub.b                   ______________________________________                                         Tricho-  9    --     --    --   --    --    --                                 derma                                                                          viride                                                                                 --    3      --     800 0.33  0.16  0.49                                       --    3      --    1000 0.33  0.20  0.53                                       --    4.5    --     400 0.50  0.08  0.58                                       --    4.5    --     800 0.50  0.16  0.66                                       --    4.5    --    1000 0.50  0.20  0.70                                       --    --     >5000 --   --    --    --                                 Pseudo- 50    --     --    --   --    --    --                                 monas                                                                          aeruginosa                                                                             --    1      --     50  0.02  0.5   0.52                                       --    2.5    --     50  0.05  0.5   0.55                                       --    5      --     50  0.1   0.5   0.60                                       --    10     --     25  0.2   0.25  0.45                                       --    10     --     50  0.2   0.5   0.70                                       --    --      100  --   --    --    --                                 ______________________________________                                    

    ______________________________________                                         Example 10                                                                     Component A = TCMTB                                                            Component B = Sorbic acid                                                             Quantities producing end points (ppm)                                   Test                                        Q.sub.A /Q.sub.a +                 organism Q.sub.a                                                                              Q.sub.A                                                                               Q.sub.b                                                                             Q.sub.B                                                                             Q.sub.A /Q.sub.a                                                                     Q.sub.B /Q.sub.b                                                                     Q.sub.B /Q.sub.b                   ______________________________________                                         Trichoderma                                                                              9    --     --   --   --    --    --                                 viride                                                                                  --    3      --   100  0.33  0.5   0.83                                        --    4.5    --    50  0.5   0.25  0.75                                        --    4.5    --   100  0.5   0.50  1.0                                         --    --     200  --   --    --    --                                 Pseudomonas                                                                             50    --     --   --   --    --    --                                 aeruginosa                                                                              --    1      --   100  0.02  0.4   0.42                                        --    2.5    --    50  0.05  0.2   0.25                                        --    2.5    --   100  0.05  0.4   0.45                                        --    5      --    50  0.1   0.2   0.3                                         --    5      --   100  0.1   0.4   0.5                                         --    10     --    5   0.2   0.02  0.22                                        --    10     --    10  0.2   0.04  0.24                                        --    10     --    25  0.2   0.1   0.3                                         --    10     --    50  0.2   0.2   0.4                                         --    10     --   100  0.2   0.4   0.6                                         --    --     250  --   --    --    --                                 ______________________________________                                    

    ______________________________________                                         Example 11                                                                     Component A = TCMTB                                                            Component B = Potassium sorbate                                                Quantities producing end points (ppm)                                          Test                                        Q.sub.A /Q.sub.a +                 organism                                                                               Q.sub.a                                                                              Q.sub.A                                                                               Q.sub.b                                                                              Q.sub.B                                                                             Q.sub.A /Q.sub.a                                                                     Q.sub.B /Q.sub.b                                                                     Q.sub.B /Q.sub.b                   ______________________________________                                         Tricho-  9    --     --    --   --    --    --                                 derma                                                                          viride                                                                                 --    1.5    --     500 0.17  0.17  0.34                                       --    3      --     500 0.33  0.17  0.50                                       --    1.5    --    1000 0.17  0.33  0.50                                       --    3      --    1000 0.33  0.33  0.66                                       --    4.5    --     500 0.50  0.17  0.67                                       --    --     >3000 --   --    --    --                                 Pseudo- Combinations against Pseudomonas aeruginosa were                       monas   not synergistic                                                        aeruginosa                                                                     ______________________________________                                    

    ______________________________________                                         Example 12                                                                     Component A = TCMTB                                                            Component B = Acetic acid                                                      Quantities producing end points (ppm)                                          Test                                        Q.sub.A /Q.sub.a +                 organism                                                                               Q.sub.a                                                                              Q.sub.A                                                                               Q.sub.b                                                                              Q.sub.B                                                                             Q.sub.A /Q.sub.a                                                                     Q.sub.B /Q.sub.b                                                                     Q.sub.B /Q.sub.b                   ______________________________________                                         Tricho-  9    --     --    --   --    --    --                                 derma                                                                          viride                                                                                 --    0.75   --    2000 0.08  0.67  0.75                                       --    1.5    --    2000 0.17  0.67  0.84                                       --    3      --     800 0.33  0.27  0.60                                       --    3      --    1000 0.33  0.33  0.66                                       --    3      --    2000 0.33  0.67  <1                                         --    4.5    --     200 0.5   0.07  0.57                                       --    4.5    --     400 0.5   0.13  0.63                                       --    4.5    --     800 0.5   0.27  0.77                                       --    4.5    --    1000 0.5   0.33  0.83                                       --    4.5    --    2000 0.5   0.67  1.12                                       --    --     >3000 --   --    --                                       Pseudo- 50    --     --    --   --    --    --                                 monas                                                                          aeruginosa                                                                             --    2.5    --     50  0.05  0.5   0.55                                       --    5      --     50  0.1   0.5   0.60                                       --    10     --     25  0.2   0.25  0.45                                       --    10     --     50  0.2   0.50  0.70                                       --    --      100  --   --    --    --                                 ______________________________________                                    

    ______________________________________                                         Example 13                                                                     Component A = TCMTB                                                            Component B = Oxalic acid                                                      Quantities producing end points (ppm)                                          Test                                        Q.sub.A /Q.sub.a +                 organism                                                                               Q.sub.a                                                                              Q.sub.A                                                                               Q.sub.b                                                                              Q.sub.B                                                                             Q.sub.A /Q.sub.a                                                                     Q.sub.B /Q.sub.b                                                                     Q.sub.B /Q.sub.b                   ______________________________________                                         Tricho-  9    --     --    --   --    --    --                                 derma                                                                          viride                                                                                 --    3      --     400 0.33  0.13  0.46                                       --    3      --     800 0.33  0.27  0.60                                       --    3      --    1000 0.33  0.33  0.66                                       --    3      --    2000 0.33  <0.67 <1                                         --    4.5    --     100 0.5   0.03  0.53                                       --    4.5    --     200 0.5   0.07  0.57                                       --    4.5    --     400 0.5   0.13  0.63                                       --    4.5    --     800 0.5   0.27  0.77                                       --    4.5    --    1000 0.5   0.33  0.83                                       --    4.5    --    2000 0.5   0.67  1.17                                       --    --     >3000 --   --    --    --                                 Pseudo- 50    --     --    --   --    --    --                                 monas                                                                          aeruginosa                                                                             --    1      --     100 0.02  0.4   0.42                                       --    2.5    --     100 0.05  0.4   0.45                                       --    5      --     100 0.1   0.4   0.5                                        --    10     --      5  0.2   0.02  0.22                                       --    10     --     10  0.2   0.04  0.24                                       --    10     --     25  0.2   0.1   0.3                                        --    10     --     50  0.2   0.2   0.4                                        --    10     --     100 0.2   0.4   0.6                                        --    --      250  --   --    --    --                                 ______________________________________                                    

    ______________________________________                                         Example 14                                                                     Component A = TCMTB                                                            Component B = Glycolic acid                                                    Quantities producing end points (ppm)                                          Test                                        Q.sub.A /Q.sub.a +                 organism                                                                               Q.sub.a                                                                              Q.sub.A                                                                               Q.sub.b                                                                              Q.sub.B                                                                             Q.sub.A /Q.sub.a                                                                     Q.sub.B /Q.sub.b                                                                     Q.sub.B /Q.sub.b                   ______________________________________                                         Tricho-  9    --     --    --   --    --    --                                 derma                                                                          viride                                                                                 --    3      --     400 0.33  0.13  0.46                                       --    3      --     800 0.33  0.27  0.60                                       --    3      --    1000 0.33  0.33  0.66                                       --    3      --    2000 0.33  <0.67 <1.0                                       --    4.5    --     25  0.5   0.00  0.50                                       --    4.5    --     50  0.5   0.02  0.52                                       --    4.5    --     100 0.5   0.03  0.53                                       --    4.5    --     200 0.5   0.07  0.57                                       --    4.5    --     400 0.5   0.13  0.63                                       --    4.5    --     800 0.5   0.27  0.77                                       --    4.5    --    1000 0.5   0.33  0.83                                       --    4.5    --    2000 0.5   0.67  1.17                                       --    --     >3000 --   --    --    --                                 Pseudo- 50    --     --    --   --    --    --                                 monas                                                                          aeruginosa                                                                             --    2.5    --     100 0.05  0.4   0.45                                       --    5      --     50  0.1   0.2   0.3                                        --    5      --     100 0.1   0.4   0.5                                        --    10     --     25  0.2   0.1   0.3                                        --    10     --     50  0.2   0.2   0.4                                        --    10     --     100 0.2   0.4   0.6                                        --    --      250  --   --    --    --                                 ______________________________________                                    

    ______________________________________                                         Example 15                                                                     Component A = TCMTB                                                            Component B = Citric acid                                                      Quantities producing end points (ppm)                                          Test                                        Q.sub.A /Q.sub.a +                 organism                                                                               Q.sub.a                                                                              Q.sub.A                                                                               Q.sub.b                                                                              Q.sub.B                                                                             Q.sub.A /Q.sub.a                                                                     Q.sub.B /Q.sub.b                                                                     Q.sub.B /Q.sub.b                   ______________________________________                                         Tricho-  9    --     --    --   --    --    --                                 derma                                                                          viride                                                                                 --    3      --     100 0.33  0.03  0.36                                       --    3      --     200 0.33  0.07  0.40                                       --    3      --     800 0.33  0.27  0.60                                       --    3      --    1000 0.33  0.33  0.66                                       --    3      --    2000 0.33  0.67  <1                                         --    4.5    --     50  0.5   0.02  0.52                                       --    4.5    --     100 0.5   0.03  0.53                                       --    4.5    --     200 0.5   0.07  0.57                                       --    4.5    --     400 0.5   0.13  0.63                                       --    4.5    --     800 0.5   0.27  0.77                                       --    4.5    --    1000 0.5   0.33  0.83                                       --    4.5    --    2000 0.5   0.67  1.17                                       --    --     >3000 --   --    --    --                                 Pseudo- 50    --     --    --   --    --    --                                 monas                                                                          aeruginosa                                                                             --    10     --     50  0.2   0.2   0.4                                        --    10     --     100 0.2   0.4   0.6                                        --    --      250  --   --    --    --                                 ______________________________________                                    

    ______________________________________                                         Example 16                                                                     Component A = TCMTB                                                            Component B = Gluconic acid                                                    Quantities producing end points (ppm)                                          Test                                        Q.sub.A /Q.sub.a +                 organism                                                                               Q.sub.a                                                                              Q.sub.A                                                                               Q.sub.b                                                                              Q.sub.B                                                                             Q.sub.A /Q.sub.a                                                                     Q.sub.B /Q.sub.b                                                                     Q.sub.B /Q.sub.b                   ______________________________________                                         Tricho-  9    --     --    --   --    --    --                                 derma                                                                          viride                                                                                 --    4.5    --     100 0.5   0.07  0.57                                       --    4.5    --     200 0.5   0.13  0.63                                       --    4.5    --     400 0.5   0.27  0.77                                       --    4.5    --     500 0.5   0.33  0.83                                       --    4.5    --    1000 0.5   0.67  1.17                                       --    --     >1500 --   --    --    --                                 Pseudo- 50    --     --    --   --    --    --                                 monas                                                                          aeruginosa                                                                             --    1      --     500 0.02  0.5   0.52                                       --    2.5    --     250 0.05  0.25  0.3                                        --    2.5    --     500 0.05  0.5   0.55                                       --    5      --     250 0.1   0.25  0.35                                       --    5      --     500 0.1   0.5   0.6                                        --    10     --     250 0.2   0.25  0.45                                       --    10     --     500 0.2   0.5   0.7                                        --    --      1000 --   --    --    --                                 ______________________________________                                    

    ______________________________________                                         Example 17                                                                     Component A = TCMTB                                                            Component B = Malic acid                                                       Quantities producing end points (ppm)                                          Test                                        Q.sub.A /Q.sub.a +                 organism                                                                               Q.sub.a                                                                              Q.sub.A                                                                               Q.sub.b                                                                              Q.sub.B                                                                             Q.sub.A /Q.sub.a                                                                     Q.sub.B /Q.sub.b                                                                     Q.sub.B /Q.sub.b                   ______________________________________                                         Tricho-  9    --     --    --   --    --    --                                 derma                                                                          viride                                                                                 --    3      --     200 0.33  0.07  0.40                                       --    3      --     400 0.33  0.13  0.46                                       --    3      --     800 0.33  0.27  0.60                                       --    3      --    1000 0.33  0.33  0.66                                       --    3      --    2000 0.33  0.67  <1                                         --    4.5    --     25  0.5   0.00  0.5                                        --    4.5    --     50  0.5   0.02  0.52                                       --    4.5    --     100 0.5   0.03  0.53                                       --    4.5    --     200 0.5   0.07  0.57                                       --    4.5    --     400 0.5   0.13  0.63                                       --    4.5    --     800 0.5   0.27  0.77                                       --    4.5    --    1000 0.5   0.33  0.83                                       --    4.5    --    2000 0.5   0.67  1.17                                       --    --     >3000 --   --    --    --                                 Pseudo- 50    --     --    --   --    --    --                                 monas                                                                          aeruginosa                                                                             --    1      --     100 0.02  0.4   0.42                                       --    2.5    --     100 0.05  0.4   0.45                                       --    5      --     25  0.1   0.1   0.2                                        --    5      --     50  0.1   0.2   0.3                                        --    5      --     100 0.1   0.4   0.5                                        --    10     --     25  0.2   0.1   0.3                                        --    10     --     50  0.2   0.2   0.4                                        --    10     --     100 0.2   0.4   0.6                                        --    --      250  --   --    --    --                                 ______________________________________                                    

    ______________________________________                                         Example 18                                                                     Component A = TCMTB                                                            Component B = Propionic acid                                                          Quantities producing end points (ppm)                                   Test                                        Q.sub.A /Q.sub.a +                 organism Q.sub.a                                                                              Q.sub.A                                                                               Q.sub.b                                                                             Q.sub.B                                                                             Q.sub.A /Q.sub.a                                                                     Q.sub.B /Q.sub.b                                                                     Q.sub.B /Q.sub.b                   ______________________________________                                         Trichoderma                                                                              9    --     --   --   --    --    --                                 viride                                                                                  --    0.75   --    800 0.08  0.4   0.48                                        --    0.75   --   1000 0.08  0.5   0.58                                        --    1.50   --    800 0.17  0.4   0.57                                        --    1.50   --   1000 0.17  0.5   0.67                                        --    3      --    400 0.33  0.20  0.53                                        --    3      --    800 0.33  0.4   0.73                                        --    3      --   1000 0.33  0.5   0.83                                        --    --     2000 --   --    --    --                                 Pseudomonas                                                                             50    --     --   --   --    --    --                                 aeruginosa                                                                              --    25     --    25  0.5   0.1   0.6                                         --    25     --    50  0.5   0.2   0.7                                         --    25     --    100 0.5   0.4   0.9                                         --    --      250 --   --    --    --                                 ______________________________________                                    

    ______________________________________                                         Example 19                                                                     Component A = TCMTB                                                            Component B = Sodium propionate                                                Quantities producing end points (ppm)                                          Test                                        Q.sub.A /Q.sub.a +                 organism                                                                               Q.sub.a                                                                              Q.sub.A                                                                               Q.sub.b                                                                              Q.sub.B                                                                             Q.sub.A /Q.sub.a                                                                     Q.sub.B /Q.sub.b                                                                     Q.sub.B /Q.sub.b                   ______________________________________                                         Tricho- 9     --     --    --   --    --    --                                 derma                                                                          viride                                                                                 --    3      --    2000 0.33  0.67  <1                                         --    4.5    --     800 0.5   0.27  0.77                                       --    4.5    --    1000 0.5   0.33  0.85                                       --    4.5    --    2000 0.5   0.67  1.12                                       --    --     >3000 --   --    --    --                                 Pseudo- Combinations against Pseudomonas aeruginosa                            monas   were not synergistic.                                                  aeruginosa                                                                     ______________________________________                                    

    ______________________________________                                         Example 20                                                                     Component A = TCMTB                                                            Component B = Lauric acid                                                      Quantities producing end points (ppm)                                          Test                                        Q.sub.A /Q.sub.a +                 organism                                                                               Q.sub.a                                                                              Q.sub.A                                                                               Q.sub.b                                                                              Q.sub.B                                                                             Q.sub.A /Q.sub.a                                                                     Q.sub.B /Q.sub.b                                                                     Q.sub.B /Q.sub.b                   ______________________________________                                         Tricho-  9    --     --    --   --    --    --                                 derma                                                                          viride                                                                                 --    3      --    1000 0.33  0.5   0.83                                       --    4.5    --     400 0.5   0.2   0.70                                       --    4.5    --     800 0.5   0.4   0.90                                       --    4.5    --    1000 0.5   0.5   1.0                                        --    --      2000 --   --    --    --                                 Pseudo- 50    --     --    --   --    --    --                                 monas                                                                          aeruginosa                                                                             --    25     --     25  0.5   0.03  0.53                                       --    25     --     50  0.5   0.0.5 0.55                                       --    25     --     100 0.5   0.1   0.6                                        --    25     --     250 0.5   0.25  0.75                                       --    25     --     500 0.5   0.5   <1                                         --    --     >1000 --   --    --    --                                 ______________________________________                                    

    ______________________________________                                         Example 21                                                                     Component A = TCMTB                                                            Component B = Undecylenic acid                                                        Quantities producing end points (ppm)                                   Test                                        Q.sub.A /Q.sub.a +                 organism Q.sub.a                                                                              Q.sub.A                                                                               Q.sub.b                                                                             Q.sub.B                                                                             Q.sub.A /Q.sub.a                                                                     Q.sub.B /Q.sub.b                                                                     Q.sub.B /Q.sub.b                   ______________________________________                                         Trichoderma                                                                              9    --     --   --   --    --    --                                 viride                                                                                  --    0.75   --   400  0.08  0.5   0.58                                        --    1.5    --   200  0.17  0.25  0.42                                        --    1.5    --   400  0.17  0.5   0.67                                        --    3.0    --    50  0.33  0.06  0.39                                        --    3.0    --   100  0.33  0.13  0.46                                        --    3.0    --   200  0.33  0.25  0.58                                        --    3.0    --   400  0.33  0.5   0.83                                        --    4.5    --    50  0.5   0.06  0.56                                        --    4.5    --   100  0.5   0.13  0.63                                        --    --     800  --   --    --    --                                 Pseudomonas                                                                             50    --     --   --   --    --    --                                 aeruginosa                                                                              --    10     --    5   0.2   0.01  0.21                                        --    10     --    10  0.2   0.02  0.22                                        --    10     --    25  0.2   0.05  0.25                                        --    10     --    50  0.2   0.1   0.30                                        --    10     --   100  0.2   0.2   0.4                                         --    10     --   250  0.2   0.5   0.7                                         --    --     500  --   --    --    --                                 ______________________________________                                    

    ______________________________________                                         Example 22                                                                     Component A = TCMTB                                                            Component B = Sodium undecylenate                                              Quantities producing end points (ppm)                                          Test                                        Q.sub.A /Q.sub.a +                 organism                                                                               Q.sub.a                                                                              Q.sub.A                                                                               Q.sub.b                                                                              Q.sub.B                                                                             Q.sub.A /Q.sub.a                                                                     Q.sub.B /Q.sub.b                                                                     Q.sub.B /Q.sub.b                   ______________________________________                                         Tricho-  9    --     --    --   --    --    --                                 derma                                                                          viride                                                                                 --    0.75   --    800  0.08  0.8   0.88                                       --    1.5    --    400  0.17  0.4   0.57                                       --    1.5    --    800  0.17  0.8   0.97                                       --    3      --    400  0.33  0.4   0.73                                       --    3      --    800  0.33  0.8   1.13                                       --    4.5    --    100  0.5   0.1   0.6                                        --    4.5    --    200  0.5   0.2   0.7                                        --    4.5    --    400  0.5   0.4   0.9                                        --    4.5    --    800  0.5   0.8   1.3                                        --    --      1000 --   --    --    --                                 Pseudo- 50    --     --    --   --    --    --                                 monas                                                                          aeruginosa                                                                             --    25     --    500  0.5   0.5   <1                                         --    --     >1000 --                                                  ______________________________________                                     

What is claimed is:
 1. A composition comprising (a) 2-(thiocyanomethylthio)benzothiazole and (b) at least one organic acid selected from the group consisting of propionic acid, a salt thereof, sodium propionate, octanoic acid, a salt thereof, nonanoic acid, a salt thereof, formic acid, a salt thereof, acetic acid, a salt thereof, lauric acid, a salt thereof, and mixtures thereof, wherein said components (a) and (b) are present in synergistic microbicidal effective amounts to control the growth of at least one microorganism selected from the group consisting of bacteria, fungi, and mixtures thereof.
 2. The composition of claim 1, wherein said bacteria or fungi is Trichoderma viride or Pseudomonas aeruginosa.
 3. The composition of claim 1, wherein the weight ratio of (a) to (b) is from about 1:99 to about 99:1.
 4. The composition of claim 3, wherein the weight ratio of (a) to (b) is from about 1:30 to about 30:1.
 5. The composition of claim 4, where the weight ratio of (a) to (b) is from about 1:5 to about 5:1.
 6. The composition of claim 1, wherein said organic acid is propionic acid or a salt thereof.
 7. The composition of claim 1, wherein said organic acid is sodium propionate.
 8. The composition of claim 1, wherein said organic acid is octanoic acid or a salt thereof.
 9. The composition of claim 1, wherein said organic acid is nonanoic acid or a salt thereof.
 10. The composition of claim 1, wherein said organic acid is formic acid or a salt thereof.
 11. The composition of claim 1, wherein said organic acid is acetic acid or a salt thereof.
 12. The composition of claim 1, wherein said organic acid is lauric acid or a salt thereof.
 13. A method of controlling the growth of at least one microorganism selected from the group consisting of bacteria and fungi in or on a material or medium susceptible to attack by the microorganism comprising the step of adding to the material or medium to control said growth a composition comprising synergistic microbicidal effective amounts of (a) 2-(thiocyanomethylthio)benzothiazole and (b) at least one organic acid selected from the group consisting of propionic acid, a salt thereof, sodium propionate, octanoic acid, a salt thereof, nonanoic acid, a salt thereof, formic acid, a salt thereof, acetic acid, a salt thereof, lauric acid, a salt thereof, and mixtures thereof.
 14. The method of claim 13, wherein said bacteria or fungi is Trichoderma viride or Pseudomonas aeruginosa.
 15. The method of claim 13, wherein said material or medium is wood pulp, wood chips, wood, lumber, paints, leathers, adhesives, coatings, animal hides, tanning liquors, paper mill liquors, metalworking fluids, starch, petrochemicals, acrylic latex paint emulsions, pharmaceutical formulations, cooling tower water, cosmetics and toiletry formulations, textiles, geological drilling lubricants or agrochemical compositions.
 16. The method of claim 13, wherein the material or medium is in the form of a solid, dispersion, emulsion or solution.
 17. The method of claim 13, wherein said components (a) and (b) can be added separately to the material or medium.
 18. The method of claim 13, wherein said organic acid is propionic acid or a salt thereof.
 19. The method of claim 13, wherein said organic acid is sodium propionate.
 20. The method of claim 13, wherein said organic acid is octanoic acid or a salt thereof.
 21. The method of claim 13, wherein said organic acid is nonanoic acid or a salt thereof.
 22. The method of claim 13, wherein said organic acid is formic acid or a salt thereof.
 23. The method of claim 13, wherein said organic acid is acetic acid or a salt thereof.
 24. The method of claim 13, wherein said organic acid is lauric acid or a salt thereof.
 25. A method for preventing spoilage of a material or medium caused by bacteria, fungi, or mixtures thereof comprising the step of adding to a material or medium to prevent spoilage a composition comprising synergistic microbicidal effective amounts of (a) 2-(thiocyanomethylthio)benzothiazole and (b) at least one organic acid selected from the group consisting of propionic acid, a salt thereof, sodium propionate, octanoic acid, a salt thereof, nonanoic acid, a salt thereof, formic acid, a salt thereof, acetic acid, a salt thereof, lauric acid, a salt thereof, and mixtures thereof.
 26. The method of claim 25, wherein said material is seeds or crops.
 27. The method of claim 25, wherein said organic acid is propionic acid or a salt thereof.
 28. The method of claim 25, wherein said organic acid is sodium propionate.
 29. The method of claim 25, wherein said organic acid is octanoic acid or a salt thereof.
 30. The method of claim 25, wherein said organic acid is nonanoic acid or a salt thereof.
 31. The method of claim 25, wherein said organic acid is formic acid or a salt thereof.
 32. The method of claim 25, wherein said organic acid is acetic acid or a salt thereof.
 33. The method of claim 25, wherein said organic acid is lauric acid or a salt thereof. 